A term referring to a woman whose appearance can range from really good looking to downright ugly. As a result, males cannot categorize such a female on a scale of 1-10 as her ranking is incredibly volatile. Thus, their attractiveness is simplified to a different scale for this rare category of women which is marked by a +1 for looking good at the time or -1 for looking bad on an occasion, hence the term ion.

Damn that girl is such an ion, yesterday I would've banged her for sure but today she looks like snooki's asshole.

Ion; the Internation Order of Ninjas.
The Internation Order of Ninjas is a non-profit organization dedicated to the betterment of ninjas world wide. They aid in the exploration of the "Theorial Plain" in which all ninjas must abide in order to gain the skills necesary for the physical, mental, and most importantly, spiritual control that one must have to live as a ninja.

No, I do not belong to the federation of killacon, but rather to the ION.

An acronym for in other news, used to abruptly segue into a different topic in the same post. In more humorous uses, it can 'ironically' segue into something actually strongly related to the first topic. Compare BTW.

... So yeah, my g/f is bound to dump me any day now. ION, Guitar Hero 3 is the awesomest thing in the history of stuff.